Put the spreadable butter, caster sugar, eggs and orange zest in a large bowl.Sift in the flour and baking powder. Beat together with a wooden spoon until evenly mixed, then scrape down the sides with a spatula and beat again.

Put a dessertspoon of cake mix in each cake case, making sure the cakes are all about the same size. Bake for about 20 minutes or until they're risen and golden brown and tops spring back when lightly pressed.

Remove and cool on a wire rack. Sift the icing sugar into a bowl and add 2tbsp orange juice.

Continue to add orange juice, a tsp at a time, until you have a thick icing that you can spoon on to the cakes.

Spoon the icing on and, while it's still wet, decorate the cakes with orange and lemon slices and silver balls.